Thermally-operated circuit breaker



Oct. 4, 1927. 1,644,443

P. B. PARKS THERMALLY OPERATED CIRCUIT BREAKER Original Filed- Feb. 19, 1925 2 Sheets-Sheet l I A i E 1644443 Oct. 4,1927. I R B. PARKS THERMALLY OPERATED CIRCUIT BREAKER Original Filed Feb. 19, 1925 ZSheets-Sheet 2 V ITlJen E);

Qg (I? @MAWMM Patented Oct. 4, 1927.

UNITED STATES PATENT OFFICE.

PAUL B. PARKS, OF OAK PARK, ILLINOIS, ASSIGNOR TO VAPOR CAR HEATING COM- IPANY, INC., OF CHICAGO, ILLINOIS, A CORPORATION OF NEW YORK.

THERMALLY-OPERATED CIRCUIT BREAKER.

Original application filed February 19,

This invention relates to a thermally operated circuit-breaker, and more particularly to an improved circuit-breaker of this type especially adapted for use in the electrical regulating mechanism for an automatically operated car heating system. The subject-matter of this application was first disclosed in my co-pending application Serial'No. 10,292, filed February 19, 1925, of which application this is a division.

- The principal object of this invention is to provide an improved circuit-breaker comprising a member which, when heated by the passage therearound of an abnormal electric current, or the unusual'prolonged passage of a normal current, is warped to operate a movable member for breaking the electric circuit.

In its preferred form, this circuit-breaker comprises a pivoted tube containing a metallic globule, which in one position of the tube bridges a pair of electric contacts, to complete an electric circuit. This circuit includes a heating coil which surrounds a bimetallic bar which is warped when unusually heated, the free end of the bar serving to tip the tube about its pivot and cause the metallic globule to move away from the contacts and break the circuit.

Other objects and advantages of this in- 'vention will be apparent from the following detailed description of one approved form of circuit breaker involving the principles of this invention.

In the accompanying drawings:

Fig. 1 is a side e evation, partially broken away, of the circuit breaker.

Fig. 2 is a plan view of the circuit breaker shown in Fig. 1.

Fig. 3 is an end view of the circuit breaker.

Fig. 4 is a perspectiveview of a portion of the adjustable clamp for pivotally supporting the mercury tube.

Fig. 5 is a diagrammatic representation of a car heating system, illustrating the operation and purpose of the improved circuit breaker forming the subject matter of this invention.

Referring first to the preferred form of the invention, as shown in Figs. 1 to 4 inclusive, an insulating base is shown at 1, on which are mounted the binding posts 2 and 3, to which the leads 4 and ,5. of the electric 1925, Serial No, 10,292. Divided and this application filed August 24, 1925. Serial No. 52,112.

circuit are connected. A lei-metallic heatsensitive bar 6 is secured at one end 7 to a lug 8 projecting upwardly from the base 1. This bar 6 is composed of two metals having difi'erent co-eflicients. of expansion, so that when heated the bar will warp in one direction. As here mounted, the bar will warp upwardly when heated, and the adjusting screw 9 which projects through the bar near its fixed end 7 into the base 1, is provided to limit or vary as desired, the upward warping of this bar when heated.

A hollow tube 10, closed at both ends, is mounted at approximately its central portion in a supporting bracket 11, pivoted at 12 in-a yoke 13, extending upwardly from the base 1, as best shown in Fig. 3. Bracket 11 comprises two similar semi-cylindrical members, each having radially upwardly. extending flanges 14 which are clamped together by screw 15 to secure the two halves of the bracket about the tube 10. By loosening this screw 15, the tube 10 may be adjusted longitudinally through the bracket 11. One of the members forming the brackproject centrally into the tube. Wire 20 is much longer than wire 19, and the inner ends of these wires are bent downwardly, as indicated at 21, and spaced slightly apart near one end of the tube 10. A globule of mercury 22 is carried within the tube 10 and is adapted to run from one end of the tube to the other as the tube is inclined one way or the other about the axis 12. When this globule of mercury is at the right-hand end of the tube, as shown in Fig. 1, the down-. turned ends 21 of wires 19 and 20 will be bridged or connected by this body of mercury so as to complete an electricalconnection therethrough. When the tube is tipped the other way, so that the globule will run to the left-hand end of the tube, the ends 21 of these wires will be out of contact with one another and'there 'will be no electrical connection therebetween. Wire 19- is connected with binding post 3 by means of the vthe flow of steam to the radiator.

flexible wire 23. Wire 20 connected through flexible wire 24 with one end of the heating coil 25, which surrounds the bimetallic bar 6, the other end of coil 25 being connected through wire 26 with the binding p A bracket 27, projecting upwardly from insulati base 1, carries an adjusting screw 28 for l i n ifiing the tilting movement of tube 10 in .the direction which breaks the circuit. A rubber-cap 29 surrounds this end of tube 10, to contact with screw 28, and serves both as a shock-absorbing and an insulating medium.

When a normal current flows through this device for a suflicient length of time, or an unusually heavy current for a shorter time, the resistance coil 25 will develop heat causing the bar 6 to warp upwardly, and since the free end of this bar is in engagement with the slotted lower end 18 of the pivoted bracket 11, the tube will be tilted toward the left, (Fig. 1), so that the mercury globule 22 -will run to the left-hand end of the tube,

thereby breaking the contact between wires 19 and 20. After the circuit is broken, the heat-sensitive bar 6 will gradually cool oh,

and will eventually return to its normal po-' sition as shown in Fig. 1, whereupon the globule 22 will run back to the right-hand end of the tube and again complete the circuit through this circuit-breaker. Although the tilting movement of tube 10 in either direction will take place quite slowly, the mercury globule 22 will run suddenly and rapidly from one end of the tube to the other when the critical angle has been reached, thereby giving the desired snap action to the circuit-breaker. The sensitiveness of bi-metallic bar 6 may be adjusted by suitably turning the screw 9, and the balance of the mercur tube 10 may be adjusted by moving the tu e longitudinally through the bracket 11.

In Fig. 5 is diagrammatically shown the electrical control mechanism for a car heating system, for use in which circuit breakers of the type hereinahove described are particularly adapted. In this system, 76 designates a radiator, and 77 a valve for controlling the circulation of heating medium through the radiator. 78 and 79 are the coils of a pair of solenoids, having a common core 80, which is connected with the operating lever 81 for the rotary valve body 82. When solenoid 79 is energized, the valve will be moved to the position shown in Fig. 9, thus causing a circulation of heating medium, such as steam from inlet pipe 83 through the radiator 76 and out through pipe 84. "When solenoid 78 is energized, the valve will be moved to cut off 85 is a high temperature thermostat, and 86 a low temperature thermostat, which are put into control of the heating system selectively by means of a switching device 87 which is operated by the presence or absence of air pressure in one of the air train lines of the car, of which pipe 88 forms an extension. 89 is a relay, the flow of. current through which is controlled by either the high temperature thermostat or the low temperature thermostat, as the case may be, this relay serving to switch current to and from the solenoid coils 78 and 79 in alternation, to operate the valve 77. All of the system so far described is shown and described in more detail in the patent to Russell 1,440,701, granted J anuary 2, 1923. In each of the operating circuits for the solenoids 78 and 7 9, is included one of the thermally operated circuit breakers hereinabove described, these being indicated at 90 and 91 respectively.

WVith the parts of the apparatus inthe positions shown in Fig. 5, the heating system is under control of the high temperature thermostat 85 with the temperature of the car below that which this thermostat is inintended to maintain and the radiator is receiving steam. Current is flowing through the relay 89 over the following circuit: from battery 92 through wire 93, resistance 94, solenoid 89, and wire 95 back to the battery. The solenoid 89 being energized, its core is raised holding the contact plate 96 up I against the fixed contacts 97 and 98, thus closing a circuit through circuit breaker 91 and valve operating solenoid 79 as follows: from the battery through wire 93, contact 97, contact plate 96, contact 98, wire 99, circuit breaker 91, wire 100, solenoid 79, wire 101, wire 102, and wire 95 back to the bat tery. However, this circuit will only be closed as long as the tube 10 is in the position shown in Fig. 1'. Assuming that the valve has just been moved to its position as shown in Fig. 5, the continued flow of current through the resistance element 25 of the circuit breaker will cause the bi-metallic bar 6 to warp upwardly to rock tube 10 and cause a movement of the mercury globule 22 from the position shown in Fig. 1 to the left hand end of the tube thus breaking the circuit. When the circuit breaker is designed for use in a system such as here described, the heat sensitive element 6 is preferably constructed so that it will be warped in something less than a minute. This gives plenty of time for the valve movement but prevents any undue heating of the solenoid coil. With the circuit broken at this pointthe bi-metallic bar will eventually cool and warp back to its original position, bringing about a reclosing of the circuit last described. Preferably the construction of the bar is such that this cooling requires a considerably longer period of time than the heating of the bar. Thus, the circuit through the solenoid coil 79 is closed at in of solenoid 79 caused by the closing of the circuit breaker 91.

WVhen the desired maximum temperature is reached, a shunt circuit through the high temperature thermostat 85 will be closed as follows: from battery 92 through wire 93, resistance 94:, wire 103, wire 104, contact 105,

mercury column 106, contact 107, wire 108,.

wire 109, and Wire 95, back to the battery. This forms a shunt circuit about the relay which will deenergize the relay coil so that contact plate 96 will drop down upon the fixed contacts 110 and 111. A circuit is now closed through the other valve-operating solenoid 78 as follows: from the battery 92 through wire 93, contact 110, contact plate 96, contact 111, wire 112, circuit breaker 90, wire 113, solenoid coil 78, wire 114, and wires 102 and 95, back to the battery. This will operate the valve to close off the flow of steam to the radiator, and the circuit breaker 90 will subsequently operate to intermittently energize the solenoid 7 8, exactly as described hereinabove in connection with oil'- cuit breaker 91.

When the low temperature thermostat 86 is in control of the system, the operations are the same as those described above, except that the radiator valve 77 is closed at a lower temperature. In the system here shown, the low temperature thermostat 86 is automatically brought into control of the system when the fluid pressure disappears from pipe 88, whereupon the contact member 115 is moved up to bridge a circuit across the spring contacts'116 and 117. This causes a shunt circuit through the low temperature thermostat 86, around high temperature thermostat 85, as follows: through wire 118, contact 116, contact 115, contact 117, wire 119, low temperature thermostat 86 and wire 1207 The remainder of the circuit is the same as described in connection with the high temperature thermostat. Since the circuit through the lower temperature thermostat 86 will be closed at a lower temperature than that through high temperature thermostat 85, the mercury column 106 of thermostat 85 will never reach the contact member 105, so that the high temperature thermostat remains idle.

t It will be noted that when used in a car heating system, such as briefly described above, the thermally operated circuit breakers forming the subject-matter of this application serve to economize on the flow of electrical energy through the operating circuits; protect the valve operating'solenoids from overheating, and also serve to intermittently energize these solenoids so as to insure keeping the valve in the desired position.

Obviously, circuit breakers of this type are adapted for various uses other than that described by way of example hereinabove, and might be used in anyv circuit which is to be intermittently broken and closed. Furthermore, by properly proportioning and adjusting the bi-metallic bar, the device may be adapted to operate only when unusually heavy currents flow through a circuit, thus operating as a fuse or safety device which will automatically again :close the circuit after an interval, by which time the dangerous current flow may have subsided.

I claim:

1. A circuit breaker comprising a heat sensitive element, an electrical resistance elecontacts within the tube adjacent one end and connected in series with the resistance element, and a free metallic globule within the tube and adapted to bridge the spaced contacts when the contact-carrying end of the tube is lowermost.

2. A circuit breaker comprising a heat sensitive element, an electrical resistance element associated therewith for warping the heat sensitive element, a rocking member connected with the heat sensitive element and gradually moved by. the heat sensitive element in response to temperature changes, a substantially horizontal closed tube carried by the rocking member, a pair of spaced contacts within the tube adjacent one end and connected in series with the resistance element, and a free metallic globule within the tube and adapted to bridge the spaced contacts when the contact-carrying end of the tube is lowermost and an adjustable stop for limiting the swinging movement of the rocking member.

8. A circuit breaker comprising a heat sensitive element, an electrical resistance element associated therewith for warping the heat sensitive element, a rocking member connected with the heat sensitive element and gradually moved by the heat sensitive element in response to temperature changes, a substantially horizontal closed tube carried intermediately by'the rocking member and adjustable longitudinally therethrough, a

pair of spaced contacts within the tube ad- 

